The aim is to improve understanding of the assessment of pain experience in patients with osteoarthritis (OA) of the knee. The current study will be divided into two parts. In Study 1, the investigators will analyse existing questionnaires relevant to the mechanisms and therapeutic targets of knee OA to establish discrete dimensions that discriminate between the different mechanisms of pain. On the basis of this analysis, the investigators will refine the questionnaires to maximise their sensitivity to knee OA. In Study 2, the investigators will seek to confirm the factor structure identified in the questionnaires in Study 1 and explore potential mediator and moderator variables between pain and quality of life using the refined measures. The investigators will also evaluate Quantitative Sensory Testing as a predictor of OA knee pain.